In pelletizing apparatus, an orifice plate forms plastic strands, the orifice plate having a distributor channel at its inlet side in the form of a grooved annular inlet. A cutting plate is provided with outlet openings which are connected to the distributor channel by inlet channels arranged around the distributor channel in successive adjoining relation. In order to improve the melt flow in the inlet region, the distributor channel has a cross-sectional width in the radial direction that is less than the radial extent of the inlet channels where they are joined to the outlet openings. The longitudinal axes of adjacent inlet channels are arranged at an angle of inclination relative to each other.
|
1. In a pelletizing apparatus having a conical supply channel for extruded melt, an orifice plate with a distributor channel at an inlet side thereof, said distributor channel being connected to said supply channel to receive extruded melt therefrom, a cutting plate on an outlet side of the orifice plate, said distributor channel being of annular shape, said cutting plate being provided with two annular rows of circumferentially spaced outlet openings from which melt strands are discharged, said rows being spaced apart in a radial direction, said orifice plate having inlet channels with first ends joined to said distributor channel and second ends joined to said outlet openings, the improvement wherein said distributor channel is constituted as an annular groove in said orifice plate having a width in the radial direction which is less than the radial spacing of the inlet channels where they are joined to said outlet openings, said inlet channels being connected to said annular groove successively in adjacent relation, alternate channels extending from said groove along longitudinal axes which are inclined relative to one another.
3. The improvement as claimed in
4. The improvement as claimed in
5. The improvement as claimed in
6. The improvement as claimed in
7. The improvement as claimed in
8. The improvement as claimed in
9. The improvement as claimed in
10. The improvement as claimed in
11. The improvement as claimed in
12. The improvement as claimed in
13. The improvement as claimed in
14. The improvement as claimed in
15. The improvement as claimed in
16. The improvement as claimed in
17. The improvement as claimed in
|
|||||||||||||||||||||||||
1. Field of the Invention
The invention relates to an orifice plate for the pelletizing of plastic strands.
More particularly, the invention relates to such an orifice plate having a distributor channel which supplies plastic melt to inlet channels which, in turn, feed the plastic melt to outlet openings from which strands of plastic melt are discharged.
2. Description of Prior Art
Orifice plates are directly connected to an extruder for producing plastic strands from an extruded melt in the underwater pelletizing process. The orifice plate has outlet openings arrayed in annular fashion in several rows or according to a specific grid in an annular field. The strands are discharged from the outlets and are periodically cut by cutters to form pellets. The distances between the outlets for the strands are relatively large, in order to avoid adherence of the separated pellets at the edges of the cutter in the case of certain products. The annular distributor channel is made correspondingly large in cross section and is arranged at the entry to the orifice plate and connected to the outlet openings via the inlet channels. This construction is shown, for example, in DE-OS 22 36 823 and is equivalent, U.S. Pat. No. 3,867,082. A disadvantage of this construction is that a low flow velocity of the melt is obtained in the distributor channel which leads to the formation of depositions and thus to product impurities.
An object of the invention is to provide an orifice plate in which depositions will be avoided in the inlet region.
This and further objects of the invention are achieved by providing the distributor channel with a width in the radial direction which is less than the radial spacing of the inlet channels whereby they are joined to said outlet openings and by inclining the longitudinal axes of adjacent inlet channels connected to the distributor channel relative to one another.
By limiting the inlet cross section of the annular inlet acting as the distributor channel to a cross-section which corresponds approximately to the cross-sectional area of the subsequent inlet channels, a sufficiently high flow velocity of the plastic melt is obtained in this region, and product depositions are avoided. A latent contamination of the flowing product with the incorporation of older deposited product particles is thereby effectively prevented. The improvement of flow velocity in the inlet region of the orifice plate is advantageously obtained by the special arrangement of the inlet channels.
DE-PS 3809735 and its equivalent U.S. Pat. No. 4,934,916 disclose the arrangement of strand outlet openings at an angle of inclination relative to their longitudinal axes in order to assure sufficient strength in the strand outlet region of the orifice plate, despite a multiplicity of strand outlet nozzles. The improvement in the inlet ratios obtained in this way by means of a common conical inlet at the entry of the strand outlet openings is without effect on the flow ratio at the inlet side of the orifice plate.
Since the construction according to the invention produces an increase in the flow velocity in the distributor channel, the product depositions that usually occur here are prevented.
In accordance with the particular embodiments of the invention, the inlet channels connected to one row of outlet openings extend parallel to a central longitudinal axis of the orifice plate whereas the inlet channels connected to a second row of outlet openings extend at an angle relative to the central longitudinal axis.
According to a further embodiment, a third row of outlet openings is provided in the cutting plate, and the inlet channels connected to the middle one of the three rows extends parallel to the central longitudinal axis while the inlet channels extending to the two outer rows are respectively inclined in opposite directions relative to the central longitudinal axis.
In order to achieve substantially corresponding cross sectional areas of the distributor channel and the inlet channels, the radial width of the distributor channel is substantially equal to the diameter of an inlet channel. The inlet channels are disposed in substantially adjoining relation along the circumferential extent of the distributor channel.
Preferably the distributor channel is formed as an annular groove at the inlet side of the orifice plate and the inlet channels open directly into the annular groove to provide smooth transitional surfaces for the flow of the melt from the distributor channel into the inlet channels.
FIG. 1 is a sectional view of a portion of a pelletizing apparatus in which an orifice plate is provided with two rows of outlet openings.
FIG. 2 is an elevational view at the inlet side of the orifice plate in FIG. 1 with the flange member removed.
FIG. 3 is a sectional view similar to FIG. 1 in which a three-row arrangement of the outlet openings is provided.
FIG. 4 is an elevational view similar to FIG. 2 for the orifice plate in FIG. 3.
FIG. 5 is an elevational view similar to FIG. 4 for a modified embodiment.
FIGS. 1 and 2 show a portion of a pelletizing apparatus which is connected to an extruder (not shown) for receiving extruded melt therefrom. The pelletizing apparatus comprises an orifice plate 1 which is connected to a flange member 5 of the extruder by bolts 2. An annular inlet channel 3 is formed between the flange 5 and the orifice plate 1 for conveying melt from the extruder to a distributor channel 19 in the orifice plate 1. Inlet channel 3 is bounded at its inner side by a conical surface 4 at the back of the orifice plate 1 and at its outer side by a corresponding conical surface of the flange member 5. The distributor channel 19 is formed as an annular groove in the back surface 22 of orifice plate 1.
Two rows of outlet openings 8, 8' for discharge of melt strands are formed on concentric circles 6, 6' within a ring-shaped cutter plate 7. The radial distance between the circles 6, 6' is relatively small. The openings 8, 8' are connected to distributor channel 19 by means of inlet channels 9, 10 extending in part in the orifice plate 1 and in part in an insert member 11. Plastic melt flows from the extruder through channel 3 to distributor channel 19 and then to inlet channels 9, 10 and outlet openings 8, 8' for discharge as individual strands. The inlet channels 9, 10 and the outlet openings 8, 8' are formed as cylindrical bore holes. Distributor channel 19 which is in the form of the groove in the back surface 22 of orifice plate 1, defines limiting surfaces 23 which lead to the inlet channels 9, 10.
A cutting knife (now shown) for separating the plastic strands discharged from outlet openings 8, 8' into pellets is located adjacent to cutting plate 7.
As further shown in FIGS. 1 and 2, the cutting plate 7 is formed as a ring of circular annulus shape and cutting plate 7 is secured to insert member 11 which is joined to orifice plate 1 by bolts 12. Heating compartments 13, 14 are provided in orifice plate 1 in the region of inlet channels 9, 10. A layer of insulating material 15 is mounted on the front surface 24 of orifice plate 1 to prevent heat loss.
Extending in part in the insert member 11 are the strand outlet openings 8, 8' and the inlet channels 9, 10, these being arranged longitudinally in axial alignment. The inlet channels 9, 10 have funnel-shaped mouth regions 16 joined to the outlet openings 8, 8'. Within the orifice plate 1 the longitudinal axes 17 and 18 of inlet channels 9 and 10 respectively are disposed adjacent to one another such that they extend individually to common hole circles 6 and 6' from the distributor channel 19. The radial width of distributor channel 19 is less than the radial spacing of inlet channels 9, 10 at the inlet region to the outlet openings 8, 8'.
In the illustrated embodiment, the longitudinal axis 17 of each inlet channel 9 extends parallel to the central, longitudinal axis 21 of the orifice plate and in axial alignment with the corresponding outlet opening 8. The longitudinal axis 18 of each inlet channel 10 extends in the orifice plate 1 at an angle of inclination relative to the longitudinal axes 17 of inlet channels 9 and outlet opening 8. The arrangement may also be one in which longitudinal axes 17, 18 of both inlet channels 9, 10 are inclined relative to the longitudinal axis of the outlet openings 8, 8' and to the longitudinal axis 21 of the orifice plate. The angle of inclination of one or both inlet channels 9, 10 is determined by the predetermined spacing between the hole circles 6, 6'.
FIG. 3 shows three rows of outlet openings 8, 8', 8" in orifice plate 1, the middle row of outlet openings being connected to inlet channels 9, which are arranged longitudinally and in axial alignment with the outlet openings 8. The adjacent outer rows of outlet openings 8' and 8" are disposed at respective opposite angles of inclination relative to the axis of middle channel 9, and are aligned with respective inlet channels 10', 10". All of the inlet channels 9, 10', 10" are individually connected to distributor channel 19 in successive adjoining relation and the radial width of channel 19 is less than the radial spacing of inlet channels 9, 10', 10" where they are joined to the outlet openings.
FIG. 5 shows an arrangement in which two middle rows of outlet openings 8, 8a are connected to respective longitudinally and axially extending inlet channels 9, 9a. The inlet channels 9, 9a are connected to respective distributor channels 19, 19a. As in the arrangement in FIG. 1, alternate inlet channels of each row are inclined as shown at 10a' and 10a" to provide two further rows of outlet openings 8a' and 8a" each associated with a respective distributor channel 19, 19a. The distributor channels 19, 19a are connected to inlet channel 3 to receive melt therefrom.
All of the disclosed embodiments provide an advantageous introduction of the melt within the distributor channel 19 or 19a at the inlet region of orifice plate 1 such that the flow velocity in this region is not substantially reduced below the flow velocity within the respective inlet channels due to limitation of the distributor channel(s) within inlet channel 3 according to the invention.
Although the invention has been described in relation to specific embodiments thereof, it will become apparent to those skilled in the art that numerous modifications and variations can be made within the scope and spirit of the invention as defined in the attached claims.
| Patent | Priority | Assignee | Title |
| 5573790, | May 13 1992 | STOROPACK, INC | Apparatus for manufacturing expandable polystyrene (EPS) pellets |
| 5650179, | Aug 23 1994 | PCD Polymere Gesellschaft m.b.H. | Apparatus for pelletizing polymers |
| 7168932, | Dec 22 2003 | Kimberly-Clark Worldwide, Inc | Apparatus for nonwoven fibrous web |
| 8876511, | Jul 11 2003 | Kobe Steel, Ltd. | Metering feeder, and system and method for kneading and extruding material |
| Patent | Priority | Assignee | Title |
| 2918701, | |||
| 3340572, | |||
| 3867082, | |||
| 3892834, | |||
| 4061462, | Jun 17 1974 | Montedison S.p.A. | Apparatus for extruding thermoplastic material |
| 4242075, | May 04 1977 | NGK Insulators, Ltd.; Institute of Technology Precision Electrical Discharge Works | Extrusion dies for extruding honeycomb structural bodies |
| 4621996, | Apr 24 1985 | GALA INDUSTRIES, INC. | Removable die center for extrusion dies |
| 4728276, | Jan 31 1986 | GALA INDUSTRIES, INC , A CORP OF VA | Underwater pelletizer |
| 4846644, | Jun 28 1988 | Whirlpool type high speed cooler for plastic grains | |
| 4934916, | Mar 23 1988 | Werner & Pfleiderer GmbH | Perforated plate for the underwater granulating of plastic strands |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Oct 05 1990 | LAMBERTUS, FRIEDRICH | Werner & Pfleiderer GmbH | ASSIGNMENT OF ASSIGNORS INTEREST | 005484 | /0794 | |
| Oct 17 1990 | Werner & Pfleiderer GmbH | (assignment on the face of the patent) | / |
| Date | Maintenance Fee Events |
| Oct 17 1995 | REM: Maintenance Fee Reminder Mailed. |
| Mar 10 1996 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
| Date | Maintenance Schedule |
| Mar 10 1995 | 4 years fee payment window open |
| Sep 10 1995 | 6 months grace period start (w surcharge) |
| Mar 10 1996 | patent expiry (for year 4) |
| Mar 10 1998 | 2 years to revive unintentionally abandoned end. (for year 4) |
| Mar 10 1999 | 8 years fee payment window open |
| Sep 10 1999 | 6 months grace period start (w surcharge) |
| Mar 10 2000 | patent expiry (for year 8) |
| Mar 10 2002 | 2 years to revive unintentionally abandoned end. (for year 8) |
| Mar 10 2003 | 12 years fee payment window open |
| Sep 10 2003 | 6 months grace period start (w surcharge) |
| Mar 10 2004 | patent expiry (for year 12) |
| Mar 10 2006 | 2 years to revive unintentionally abandoned end. (for year 12) |